This invention relates to the production of superhard products such as diamond, polycrystalline diamond, and cubic boron nitride produced by the high pressure and high temperature (HPHT) method. More particularly this invention relates to the HPHT containers or can assemblies in which superhard materials are processed. Superhard materials produced by the HPHT method are generally formed by encapsulating raw ingredients into a container, variously known in the art as a container, a can, an enclosure, a cup, a shield, or a tube.
A meltable sealant may be melted to seal the can. An area of ongoing research within the field of meltable sealant sealing is into methods to prevent the meltable sealant from flowing into the mixture of raw ingredients and causing contamination. One method that may prevent the contamination of the mixture is the use of an anti-wetting material such as stop-off. An anti-wetting material performs the function of arresting the wetting of a liquid onto a solid. With respect to a meltable sealant, an anti-wetting agent may hinder the spread of the melted meltable sealant. Anti-wetting materials have taken the form of a solid plate or disc. However, anti-wetting plates or discs must be precisely cut and shaped to fit into the can to allow for impurities to leave the diamond and to prevent meltable sealant from contaminating the diamond. Additionally, the process of manufacturing and using stop-off discs may be costly and due to improperly fitted discs may lead to low yields.
U.S. Pat. No. 4,333,902 to Hara which is herein incorporated by reference for all that it contains, discloses a process of producing a sintered compact comprising filling a cup with a powdered material to be sintered, putting on an opening of the cup a covering member consisting of a lid and solder so as to permit ventilation between the interior and exterior of the cup to form a cup assembly, applying heat as well as vacuum to the cup assembly to degas the powdered material, melting the solder by the continuation of heat to air-tightly seal the cup with the lid to obtain a closed cup compressible under high pressure at high temperature while maintaining the air-tight seal, and hot-pressing the closed cup to obtain a sintered compact. The covering member may include a porous lid closing the cup and a solder put on the porous lid.
U.S. Pat. No. 4,425,315 to Tsuji, et al. which is herein incorporated by reference for all that it contains, discloses a diamond sintered compact wherein diamond crystal particles are uniformly orientated in a particular direction and the method for producing the same, and has for an object to provide a diamond sintered compact having a high thermal conductivity particularly suitable for heat sink for use in the field of electronics. According to the invention, graphite is used as carbonaceous raw material, diamond crystal particles having such elongated shape that the ratio of the length of the long axis to that of the short axis is more than 2 being synthesized in such state that the greater part of the crystal particles have their long axes uniformly oriented in a particular direction, the crystal particles being sintered in the direction of the long axes thereof so that transformation of the graphite into diamond and sintering thereof may be accomplished synchronously. The invention has for an object to obtain a diamond sintered compact suitable for the aforesaid use by degassing reaction system raw material plugged into an air permeable container by heating it in vacuum in order to intercept gaseous components causing a decrease of thermal conductivity at the time of synthesizing diamond from carbonaceous material and a catalytic metal and sintering thereof, subsequently the air permeable part of the said container being sealed by means of soldering material preliminarily placed in contact with the said container.
U.S. Pat. No. 6,596,225 to Pope, et al. which is herein incorporated by reference for all that it contains, discloses sealing of the can by electron beam welding at high temperature and in a vacuum.
U.S. Patent Publication No. 2005/0044800 to Hall, et al. which is herein incorporated by reference for all that it contains, discloses an assembly for High-Pressure High-Temperature (HPHT) processing comprising a can, a cap, a meltable sealant and sealant barrier, and a superhard mixture comprising superhard particles. The superhard particles may be positioned adjacent a substrate of cemented metal carbide. The can and cap contain the superhard mixture with the sealant barrier positioned within the assembly so as to be intermediate the sealant and at least a portion of the mixture, thereby preventing the sealant from coming in contact with the mixture during processing. The assembly is placed within a vacuum chamber and heated to a temperature sufficient to cleanse the assembly and then melt the sealant providing a hermetic seal for the assembly in preparation for further HPHT processing.
U.S. Patent Publication No. 2008/0057145 to Hall, et al. which is herein incorporated by reference for all that it contains discloses an improved assembly for HPHT processing having a can with an opening and a mixture disposed within the opening. A sealant barrier is positioned atop the mixture. First and second lids are positioned atop the mixture. A meltable sealant positioned intermediate the second lid and a cap covering the opening.
Not withstanding the preceding patents, there remains a need in the art for an easier and more cost effective method of preventing meltable sealant contamination within the can.